The project aims broadly to characterize the perception of odorants and irritants both singly and in combination. Matters of interest include: (a) role of preneural factors (e.g., filtering influence of mucus), (b) additivity and interaction of chemosensations, (c) clinical assessment of chemosensory functioning, and (d) role of environmental variables. The work has relevance to industrial exposures to airborne materials, particularly irritants. Experiments planned for the current year include: (a) exploration of individual differences in sensitivity to irritants as assessed by reflex changes in inhalation, (b) measurement of reaction time to irritants in order to decide the effective depth of the receptors and in order to search for physicochemical correlates of common chemical stimulation, (c) exploration of the central neural locus of olfactory adaptation (i.e., how well an adapting stimulus presented unilaterally will generalize its desensitizing influence to the contralateral side under conditions of self-adaptation and cross-adaptation), and (d) exploration of the commonality among odorants by means of a pedestal technique. This technique requires persons to detect small increments in the concentration of a test stimulus perceived against a background of ongoing stimulation. The procedure brings a variety of interrelated sensory phenomena (masking, similarity of odor quality, adaptation, combinatorial rules of mixtures) to bear on the search for commonality.